Circuit arrangement for relays



Jan. 21, 1969 H. BECHLER 3,423,639

- cmcun ARRANGEMENT FOR RELAYS Filed Aug. 17, 1965 Z QTELECOMMUNICATIONS LINE Fig.2 v Fig.3 Fig.4

United States Patent 3,423,639 CIRCUIT ARRANGEMENT FOR RELAYS HorstBechler, Stuttgart-Zutfenhausen, Germany, assignor to InternationalStandard Electric Corporation, New York, N.Y., a corporation of DelawareFiled Aug. 17, 1965, Ser. No. 480,451 Claims priority, appligation(slgrmany, Sept. 9, 1964,

Us. 01. 317-123 1 Claim Int. Cl. H01]: 47/00 ABSTRACT OF THE DISCLOSUREThe invention relates to circuits including a relay operated by acontrol switch and particularly to means for compensating for capacitiveimpedances of different magnitude in parallel with lines connecting thecontrol switch to the relay.

Prior art systems to which this invention applies include a checkingfacility, equipped with a relay, for measuring pulses from a remotepulse contact via loaded lines of a telecommunication system. Thereby inthe course of the line different transmissions or different lines can bealternately switched into the system causing capacitive impedanees ofdifferent magnitudes to be placed in parallel to the pulse contact. Suchcapacitive impedances, being in parallel to the pulse contact and havingvarious different magnitudes, cause the release or dropping periods ofthe relay of the checking facility to vary in length so that properchecking of the pulse contact is impossible.

In another relay arrangement known to the art the control contact isbridged for spark-quenching through an R/C-element. But here theR/C-element is firmly associated with the control contact and with therelay. Dimensioning of the R/C-element thereby depends on the magnitureof the relay impedance, so that a defined delay in the release of therelay can be assumed and thereby measures can be taken to balance thepulse distortions with the aid of succeeding facilities.

It is moreover, known that by a choke coil, shunted to the relay, inwhich the stored magnetic energy is higher than the one for the relay,said relay can be dropped quicker as would be the case when it isswitched off.

A primary object of the invention is to provide a circuit arrangementfor relays in which the pulse distortions of the relay, caused bydifferently large capacitive impedances parallel to the control switch,are essentially reduced. This is achieved according to the invention byapplying the aforementioned measure that a choke coil is inserted inparallel to such a relay, the stored magnetic energy being higher thanthe one selected for the relay.

According to a further embodiment of the invention, the stored magneticenergy is essentially larger for the choke coil, for example, threetimes as large as the one "ice selected for the relay, in order toreduce the influence of the capacitive component of the impedance,parallel to the control switch, on the release delay of the relay.

When the controlled relay is an unpoled one, the negative currentproduced in such a relay by the choke coil may cause under certaincircumstances a re-energizing of such a relay for a short time.Therefore, and in compliance with a further embodiment of the invention,a poled rectifier is series-connected with the relay in the direction ofthe control current.

The invention is now in detail explained with the aid of an example.

FIG. 1 shows a circuit arrangement to test, for example a control switchx (which may be an electronic switch) via a telecommunication line,having a capacitive impedance Z. The test equipment includes a relay Awith which the pulses of the control switch at (in this case a relaycontact) shall be determined. Series-connected with the relay A is arectifier G and in parallel to said seriesconnection a choke-coil D isprovided.

The arrangement will be considered at first without the rectifier G andthe impedance Z.

The stored magnetic energy /2L I of the choke coil D is selected to behigher than the stored magnetic energy /2L J of the relay, so that theswitch-01f current i of the relay becomes negative, as shown in FIG. 2.

L and I represent the inductivity and the operating current of the relayA and L I represent the inductivity and the operating current of thechoke coil D. In FIG. 2, the relay current very steeply drops from thestarting value i to the negative value i and thereupon slowly returns tothe value Zero. When an impedance Z of varying magnitude is in parallelwith the line from the con-tact x the switch-off curve according to FIG.3 is not as steep as the curve shown in FIG. 2, but compared with anarrangement without choke coil D it is much steeper, so that theinfluence of the impedances Z on the pulse distortion of the relay A isessentially reduced.

For further improvement of the arrangement the stored magnetic energy1/ZLDJD2 is made even higher, for example three times higher than thestored magnetic energy /2L J so that the switch-off curve, shown in FIG.3 will be nearly as steep as the one shown in FIG. 1.

For relay A either a poled or a non-poled relay can be used. A non-poledrelay can be energized again under certain circumstances at theaforementioned dimensioning, at least for a short time. Therefore, therectifier G is provided to block the relay current in the negativedirection. Thereby the switch-off curve according to FIG. 4 is obtained,the steepness of which is largely independent of the magnitude of thecapacitive component of the impedance Z, so that the pulse distortion ofthe relay A remains extremely small, even due to the impedance Z.

While the principles of the invention have been described above inconnection with specific apparatus and applications, it is to beunderstood that this description is made only by way of example and notas a limitation on the scope of the invention.

What is claimed is:

1. A circuit arrangement for a relay coupled to a central switch throughmeans exhibiting different amounts of capacitive reactance, said circuitcomprising:

a control switch,

a relay,

means having capacitive reactance connecting said control switch to saidrelay,

a choke coil connected in parallel to said relay, said choke coil havingthe capability of storing greater amounts of magnetic energy than canthe relay, and

a rectifier inserted in series between said switch and said relay, saidrectifier being poled in a direction permitting control current to flowonly from the switch to the relay.

5 LEE T. HIX, Primary Examiner.

US. Cl. X.R.

